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linux/mm/huge_memory.c
Kirill A. Shutemov 79553da293 thp: cleanup khugepaged startup 
Few trivial cleanups:

 - no need to call set_recommended_min_free_kbytes() from
   late_initcall() -- start_khugepaged() calls it;

 - no need to call set_recommended_min_free_kbytes() from
   start_khugepaged() if khugepaged is not started;

 - there isn't much point in running start_khugepaged() if we've just
   set transparent_hugepage_flags to zero;

 - start_khugepaged() is misnamed -- it also used to stop the thread;

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-04-15 16:35:19 -07:00

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/*
* Copyright (C) 2009 Red Hat, Inc.
*
* This work is licensed under the terms of the GNU GPL, version 2. See
* the COPYING file in the top-level directory.
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/highmem.h>
#include <linux/hugetlb.h>
#include <linux/mmu_notifier.h>
#include <linux/rmap.h>
#include <linux/swap.h>
#include <linux/shrinker.h>
#include <linux/mm_inline.h>
#include <linux/kthread.h>
#include <linux/khugepaged.h>
#include <linux/freezer.h>
#include <linux/mman.h>
#include <linux/pagemap.h>
#include <linux/migrate.h>
#include <linux/hashtable.h>
#include <asm/tlb.h>
#include <asm/pgalloc.h>
#include "internal.h"
/*
* By default transparent hugepage support is disabled in order that avoid
* to risk increase the memory footprint of applications without a guaranteed
* benefit. When transparent hugepage support is enabled, is for all mappings,
* and khugepaged scans all mappings.
* Defrag is invoked by khugepaged hugepage allocations and by page faults
* for all hugepage allocations.
*/
unsigned long transparent_hugepage_flags __read_mostly =
#ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
(1<<TRANSPARENT_HUGEPAGE_FLAG)|
#endif
#ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
(1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
#endif
(1<<TRANSPARENT_HUGEPAGE_DEFRAG_FLAG)|
(1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)|
(1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
/* default scan 8*512 pte (or vmas) every 30 second */
static unsigned int khugepaged_pages_to_scan __read_mostly = HPAGE_PMD_NR*8;
static unsigned int khugepaged_pages_collapsed;
static unsigned int khugepaged_full_scans;
static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000;
/* during fragmentation poll the hugepage allocator once every minute */
static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000;
static struct task_struct *khugepaged_thread __read_mostly;
static DEFINE_MUTEX(khugepaged_mutex);
static DEFINE_SPINLOCK(khugepaged_mm_lock);
static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait);
/*
* default collapse hugepages if there is at least one pte mapped like
* it would have happened if the vma was large enough during page
* fault.
*/
static unsigned int khugepaged_max_ptes_none __read_mostly = HPAGE_PMD_NR-1;
static int khugepaged(void *none);
static int khugepaged_slab_init(void);
static void khugepaged_slab_exit(void);
#define MM_SLOTS_HASH_BITS 10
static __read_mostly DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS);
static struct kmem_cache *mm_slot_cache __read_mostly;
/**
* struct mm_slot - hash lookup from mm to mm_slot
* @hash: hash collision list
* @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head
* @mm: the mm that this information is valid for
*/
struct mm_slot {
struct hlist_node hash;
struct list_head mm_node;
struct mm_struct *mm;
};
/**
* struct khugepaged_scan - cursor for scanning
* @mm_head: the head of the mm list to scan
* @mm_slot: the current mm_slot we are scanning
* @address: the next address inside that to be scanned
*
* There is only the one khugepaged_scan instance of this cursor structure.
*/
struct khugepaged_scan {
struct list_head mm_head;
struct mm_slot *mm_slot;
unsigned long address;
};
static struct khugepaged_scan khugepaged_scan = {
.mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head),
};
static int set_recommended_min_free_kbytes(void)
{
struct zone *zone;
int nr_zones = 0;
unsigned long recommended_min;
for_each_populated_zone(zone)
nr_zones++;
/* Make sure at least 2 hugepages are free for MIGRATE_RESERVE */
recommended_min = pageblock_nr_pages * nr_zones * 2;
/*
* Make sure that on average at least two pageblocks are almost free
* of another type, one for a migratetype to fall back to and a
* second to avoid subsequent fallbacks of other types There are 3
* MIGRATE_TYPES we care about.
*/
recommended_min += pageblock_nr_pages * nr_zones *
MIGRATE_PCPTYPES * MIGRATE_PCPTYPES;
/* don't ever allow to reserve more than 5% of the lowmem */
recommended_min = min(recommended_min,
(unsigned long) nr_free_buffer_pages() / 20);
recommended_min <<= (PAGE_SHIFT-10);
if (recommended_min > min_free_kbytes) {
if (user_min_free_kbytes >= 0)
pr_info("raising min_free_kbytes from %d to %lu "
"to help transparent hugepage allocations\n",
min_free_kbytes, recommended_min);
min_free_kbytes = recommended_min;
}
setup_per_zone_wmarks();
return 0;
}
static int start_stop_khugepaged(void)
{
int err = 0;
if (khugepaged_enabled()) {
if (!khugepaged_thread)
khugepaged_thread = kthread_run(khugepaged, NULL,
"khugepaged");
if (unlikely(IS_ERR(khugepaged_thread))) {
pr_err("khugepaged: kthread_run(khugepaged) failed\n");
err = PTR_ERR(khugepaged_thread);
khugepaged_thread = NULL;
goto fail;
}
if (!list_empty(&khugepaged_scan.mm_head))
wake_up_interruptible(&khugepaged_wait);
set_recommended_min_free_kbytes();
} else if (khugepaged_thread) {
kthread_stop(khugepaged_thread);
khugepaged_thread = NULL;
}
fail:
return err;
}
static atomic_t huge_zero_refcount;
struct page *huge_zero_page __read_mostly;
static inline bool is_huge_zero_pmd(pmd_t pmd)
{
return is_huge_zero_page(pmd_page(pmd));
}
static struct page *get_huge_zero_page(void)
{
struct page *zero_page;
retry:
if (likely(atomic_inc_not_zero(&huge_zero_refcount)))
return READ_ONCE(huge_zero_page);
zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE,
HPAGE_PMD_ORDER);
if (!zero_page) {
count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED);
return NULL;
}
count_vm_event(THP_ZERO_PAGE_ALLOC);
preempt_disable();
if (cmpxchg(&huge_zero_page, NULL, zero_page)) {
preempt_enable();
__free_pages(zero_page, compound_order(zero_page));
goto retry;
}
/* We take additional reference here. It will be put back by shrinker */
atomic_set(&huge_zero_refcount, 2);
preempt_enable();
return READ_ONCE(huge_zero_page);
}
static void put_huge_zero_page(void)
{
/*
* Counter should never go to zero here. Only shrinker can put
* last reference.
*/
BUG_ON(atomic_dec_and_test(&huge_zero_refcount));
}
static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink,
struct shrink_control *sc)
{
/* we can free zero page only if last reference remains */
return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0;
}
static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink,
struct shrink_control *sc)
{
if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) {
struct page *zero_page = xchg(&huge_zero_page, NULL);
BUG_ON(zero_page == NULL);
__free_pages(zero_page, compound_order(zero_page));
return HPAGE_PMD_NR;
}
return 0;
}
static struct shrinker huge_zero_page_shrinker = {
.count_objects = shrink_huge_zero_page_count,
.scan_objects = shrink_huge_zero_page_scan,
.seeks = DEFAULT_SEEKS,
};
#ifdef CONFIG_SYSFS
static ssize_t double_flag_show(struct kobject *kobj,
struct kobj_attribute *attr, char *buf,
enum transparent_hugepage_flag enabled,
enum transparent_hugepage_flag req_madv)
{
if (test_bit(enabled, &transparent_hugepage_flags)) {
VM_BUG_ON(test_bit(req_madv, &transparent_hugepage_flags));
return sprintf(buf, "[always] madvise never\n");
} else if (test_bit(req_madv, &transparent_hugepage_flags))
return sprintf(buf, "always [madvise] never\n");
else
return sprintf(buf, "always madvise [never]\n");
}
static ssize_t double_flag_store(struct kobject *kobj,
struct kobj_attribute *attr,
const char *buf, size_t count,
enum transparent_hugepage_flag enabled,
enum transparent_hugepage_flag req_madv)
{
if (!memcmp("always", buf,
min(sizeof("always")-1, count))) {
set_bit(enabled, &transparent_hugepage_flags);
clear_bit(req_madv, &transparent_hugepage_flags);
} else if (!memcmp("madvise", buf,
min(sizeof("madvise")-1, count))) {
clear_bit(enabled, &transparent_hugepage_flags);
set_bit(req_madv, &transparent_hugepage_flags);
} else if (!memcmp("never", buf,
min(sizeof("never")-1, count))) {
clear_bit(enabled, &transparent_hugepage_flags);
clear_bit(req_madv, &transparent_hugepage_flags);
} else
return -EINVAL;
return count;
}
static ssize_t enabled_show(struct kobject *kobj,
struct kobj_attribute *attr, char *buf)
{
return double_flag_show(kobj, attr, buf,
TRANSPARENT_HUGEPAGE_FLAG,
TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
}
static ssize_t enabled_store(struct kobject *kobj,
struct kobj_attribute *attr,
const char *buf, size_t count)
{
ssize_t ret;
ret = double_flag_store(kobj, attr, buf, count,
TRANSPARENT_HUGEPAGE_FLAG,
TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
if (ret > 0) {
int err;
mutex_lock(&khugepaged_mutex);
err = start_stop_khugepaged();
mutex_unlock(&khugepaged_mutex);
if (err)
ret = err;
}
return ret;
}
static struct kobj_attribute enabled_attr =
__ATTR(enabled, 0644, enabled_show, enabled_store);
static ssize_t single_flag_show(struct kobject *kobj,
struct kobj_attribute *attr, char *buf,
enum transparent_hugepage_flag flag)
{
return sprintf(buf, "%d\n",
!!test_bit(flag, &transparent_hugepage_flags));
}
static ssize_t single_flag_store(struct kobject *kobj,
struct kobj_attribute *attr,
const char *buf, size_t count,
enum transparent_hugepage_flag flag)
{
unsigned long value;
int ret;
ret = kstrtoul(buf, 10, &value);
if (ret < 0)
return ret;
if (value > 1)
return -EINVAL;
if (value)
set_bit(flag, &transparent_hugepage_flags);
else
clear_bit(flag, &transparent_hugepage_flags);
return count;
}
/*
* Currently defrag only disables __GFP_NOWAIT for allocation. A blind
* __GFP_REPEAT is too aggressive, it's never worth swapping tons of
* memory just to allocate one more hugepage.
*/
static ssize_t defrag_show(struct kobject *kobj,
struct kobj_attribute *attr, char *buf)
{
return double_flag_show(kobj, attr, buf,
TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
}
static ssize_t defrag_store(struct kobject *kobj,
struct kobj_attribute *attr,
const char *buf, size_t count)
{
return double_flag_store(kobj, attr, buf, count,
TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
}
static struct kobj_attribute defrag_attr =
__ATTR(defrag, 0644, defrag_show, defrag_store);
static ssize_t use_zero_page_show(struct kobject *kobj,
struct kobj_attribute *attr, char *buf)
{
return single_flag_show(kobj, attr, buf,
TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
}
static ssize_t use_zero_page_store(struct kobject *kobj,
struct kobj_attribute *attr, const char *buf, size_t count)
{
return single_flag_store(kobj, attr, buf, count,
TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
}
static struct kobj_attribute use_zero_page_attr =
__ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store);
#ifdef CONFIG_DEBUG_VM
static ssize_t debug_cow_show(struct kobject *kobj,
struct kobj_attribute *attr, char *buf)
{
return single_flag_show(kobj, attr, buf,
TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
}
static ssize_t debug_cow_store(struct kobject *kobj,
struct kobj_attribute *attr,
const char *buf, size_t count)
{
return single_flag_store(kobj, attr, buf, count,
TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
}
static struct kobj_attribute debug_cow_attr =
__ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
#endif /* CONFIG_DEBUG_VM */
static struct attribute *hugepage_attr[] = {
&enabled_attr.attr,
&defrag_attr.attr,
&use_zero_page_attr.attr,
#ifdef CONFIG_DEBUG_VM
&debug_cow_attr.attr,
#endif
NULL,
};
static struct attribute_group hugepage_attr_group = {
.attrs = hugepage_attr,
};
static ssize_t scan_sleep_millisecs_show(struct kobject *kobj,
struct kobj_attribute *attr,
char *buf)
{
return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs);
}
static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
struct kobj_attribute *attr,
const char *buf, size_t count)
{
unsigned long msecs;
int err;
err = kstrtoul(buf, 10, &msecs);
if (err || msecs > UINT_MAX)
return -EINVAL;
khugepaged_scan_sleep_millisecs = msecs;
wake_up_interruptible(&khugepaged_wait);
return count;
}
static struct kobj_attribute scan_sleep_millisecs_attr =
__ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show,
scan_sleep_millisecs_store);
static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj,
struct kobj_attribute *attr,
char *buf)
{
return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs);
}
static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj,
struct kobj_attribute *attr,
const char *buf, size_t count)
{
unsigned long msecs;
int err;
err = kstrtoul(buf, 10, &msecs);
if (err || msecs > UINT_MAX)
return -EINVAL;
khugepaged_alloc_sleep_millisecs = msecs;
wake_up_interruptible(&khugepaged_wait);
return count;
}
static struct kobj_attribute alloc_sleep_millisecs_attr =
__ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show,
alloc_sleep_millisecs_store);
static ssize_t pages_to_scan_show(struct kobject *kobj,
struct kobj_attribute *attr,
char *buf)
{
return sprintf(buf, "%u\n", khugepaged_pages_to_scan);
}
static ssize_t pages_to_scan_store(struct kobject *kobj,
struct kobj_attribute *attr,
const char *buf, size_t count)
{
int err;
unsigned long pages;
err = kstrtoul(buf, 10, &pages);
if (err || !pages || pages > UINT_MAX)
return -EINVAL;
khugepaged_pages_to_scan = pages;
return count;
}
static struct kobj_attribute pages_to_scan_attr =
__ATTR(pages_to_scan, 0644, pages_to_scan_show,
pages_to_scan_store);
static ssize_t pages_collapsed_show(struct kobject *kobj,
struct kobj_attribute *attr,
char *buf)
{
return sprintf(buf, "%u\n", khugepaged_pages_collapsed);
}
static struct kobj_attribute pages_collapsed_attr =
__ATTR_RO(pages_collapsed);
static ssize_t full_scans_show(struct kobject *kobj,
struct kobj_attribute *attr,
char *buf)
{
return sprintf(buf, "%u\n", khugepaged_full_scans);
}
static struct kobj_attribute full_scans_attr =
__ATTR_RO(full_scans);
static ssize_t khugepaged_defrag_show(struct kobject *kobj,
struct kobj_attribute *attr, char *buf)
{
return single_flag_show(kobj, attr, buf,
TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
}
static ssize_t khugepaged_defrag_store(struct kobject *kobj,
struct kobj_attribute *attr,
const char *buf, size_t count)
{
return single_flag_store(kobj, attr, buf, count,
TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
}
static struct kobj_attribute khugepaged_defrag_attr =
__ATTR(defrag, 0644, khugepaged_defrag_show,
khugepaged_defrag_store);
/*
* max_ptes_none controls if khugepaged should collapse hugepages over
* any unmapped ptes in turn potentially increasing the memory
* footprint of the vmas. When max_ptes_none is 0 khugepaged will not
* reduce the available free memory in the system as it
* runs. Increasing max_ptes_none will instead potentially reduce the
* free memory in the system during the khugepaged scan.
*/
static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj,
struct kobj_attribute *attr,
char *buf)
{
return sprintf(buf, "%u\n", khugepaged_max_ptes_none);
}
static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj,
struct kobj_attribute *attr,
const char *buf, size_t count)
{
int err;
unsigned long max_ptes_none;
err = kstrtoul(buf, 10, &max_ptes_none);
if (err || max_ptes_none > HPAGE_PMD_NR-1)
return -EINVAL;
khugepaged_max_ptes_none = max_ptes_none;
return count;
}
static struct kobj_attribute khugepaged_max_ptes_none_attr =
__ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show,
khugepaged_max_ptes_none_store);
static struct attribute *khugepaged_attr[] = {
&khugepaged_defrag_attr.attr,
&khugepaged_max_ptes_none_attr.attr,
&pages_to_scan_attr.attr,
&pages_collapsed_attr.attr,
&full_scans_attr.attr,
&scan_sleep_millisecs_attr.attr,
&alloc_sleep_millisecs_attr.attr,
NULL,
};
static struct attribute_group khugepaged_attr_group = {
.attrs = khugepaged_attr,
.name = "khugepaged",
};
static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
{
int err;
*hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
if (unlikely(!*hugepage_kobj)) {
pr_err("failed to create transparent hugepage kobject\n");
return -ENOMEM;
}
err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
if (err) {
pr_err("failed to register transparent hugepage group\n");
goto delete_obj;
}
err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
if (err) {
pr_err("failed to register transparent hugepage group\n");
goto remove_hp_group;
}
return 0;
remove_hp_group:
sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
delete_obj:
kobject_put(*hugepage_kobj);
return err;
}
static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
{
sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
kobject_put(hugepage_kobj);
}
#else
static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
{
return 0;
}
static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
{
}
#endif /* CONFIG_SYSFS */
static int __init hugepage_init(void)
{
int err;
struct kobject *hugepage_kobj;
if (!has_transparent_hugepage()) {
transparent_hugepage_flags = 0;
return -EINVAL;
}
err = hugepage_init_sysfs(&hugepage_kobj);
if (err)
goto err_sysfs;
err = khugepaged_slab_init();
if (err)
goto err_slab;
err = register_shrinker(&huge_zero_page_shrinker);
if (err)
goto err_hzp_shrinker;
/*
* By default disable transparent hugepages on smaller systems,
* where the extra memory used could hurt more than TLB overhead
* is likely to save. The admin can still enable it through /sys.
*/
if (totalram_pages < (512 << (20 - PAGE_SHIFT))) {
transparent_hugepage_flags = 0;
return 0;
}
err = start_stop_khugepaged();
if (err)
goto err_khugepaged;
return 0;
err_khugepaged:
unregister_shrinker(&huge_zero_page_shrinker);
err_hzp_shrinker:
khugepaged_slab_exit();
err_slab:
hugepage_exit_sysfs(hugepage_kobj);
err_sysfs:
return err;
}
subsys_initcall(hugepage_init);
static int __init setup_transparent_hugepage(char *str)
{
int ret = 0;
if (!str)
goto out;
if (!strcmp(str, "always")) {
set_bit(TRANSPARENT_HUGEPAGE_FLAG,
&transparent_hugepage_flags);
clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
&transparent_hugepage_flags);
ret = 1;
} else if (!strcmp(str, "madvise")) {
clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
&transparent_hugepage_flags);
set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
&transparent_hugepage_flags);
ret = 1;
} else if (!strcmp(str, "never")) {
clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
&transparent_hugepage_flags);
clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
&transparent_hugepage_flags);
ret = 1;
}
out:
if (!ret)
pr_warn("transparent_hugepage= cannot parse, ignored\n");
return ret;
}
__setup("transparent_hugepage=", setup_transparent_hugepage);
pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
{
if (likely(vma->vm_flags & VM_WRITE))
pmd = pmd_mkwrite(pmd);
return pmd;
}
static inline pmd_t mk_huge_pmd(struct page *page, pgprot_t prot)
{
pmd_t entry;
entry = mk_pmd(page, prot);
entry = pmd_mkhuge(entry);
return entry;
}
static int __do_huge_pmd_anonymous_page(struct mm_struct *mm,
struct vm_area_struct *vma,
unsigned long haddr, pmd_t *pmd,
struct page *page, gfp_t gfp)
{
struct mem_cgroup *memcg;
pgtable_t pgtable;
spinlock_t *ptl;
VM_BUG_ON_PAGE(!PageCompound(page), page);
if (mem_cgroup_try_charge(page, mm, gfp, &memcg))
return VM_FAULT_OOM;
pgtable = pte_alloc_one(mm, haddr);
if (unlikely(!pgtable)) {
mem_cgroup_cancel_charge(page, memcg);
return VM_FAULT_OOM;
}
clear_huge_page(page, haddr, HPAGE_PMD_NR);
/*
* The memory barrier inside __SetPageUptodate makes sure that
* clear_huge_page writes become visible before the set_pmd_at()
* write.
*/
__SetPageUptodate(page);
ptl = pmd_lock(mm, pmd);
if (unlikely(!pmd_none(*pmd))) {
spin_unlock(ptl);
mem_cgroup_cancel_charge(page, memcg);
put_page(page);
pte_free(mm, pgtable);
} else {
pmd_t entry;
entry = mk_huge_pmd(page, vma->vm_page_prot);
entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
page_add_new_anon_rmap(page, vma, haddr);
mem_cgroup_commit_charge(page, memcg, false);
lru_cache_add_active_or_unevictable(page, vma);
pgtable_trans_huge_deposit(mm, pmd, pgtable);
set_pmd_at(mm, haddr, pmd, entry);
add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
atomic_long_inc(&mm->nr_ptes);
spin_unlock(ptl);
}
return 0;
}
static inline gfp_t alloc_hugepage_gfpmask(int defrag, gfp_t extra_gfp)
{
return (GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_WAIT)) | extra_gfp;
}
/* Caller must hold page table lock. */
static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
struct page *zero_page)
{
pmd_t entry;
if (!pmd_none(*pmd))
return false;
entry = mk_pmd(zero_page, vma->vm_page_prot);
entry = pmd_mkhuge(entry);
pgtable_trans_huge_deposit(mm, pmd, pgtable);
set_pmd_at(mm, haddr, pmd, entry);
atomic_long_inc(&mm->nr_ptes);
return true;
}
int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
unsigned long address, pmd_t *pmd,
unsigned int flags)
{
gfp_t gfp;
struct page *page;
unsigned long haddr = address & HPAGE_PMD_MASK;
if (haddr < vma->vm_start || haddr + HPAGE_PMD_SIZE > vma->vm_end)
return VM_FAULT_FALLBACK;
if (unlikely(anon_vma_prepare(vma)))
return VM_FAULT_OOM;
if (unlikely(khugepaged_enter(vma, vma->vm_flags)))
return VM_FAULT_OOM;
if (!(flags & FAULT_FLAG_WRITE) && !mm_forbids_zeropage(mm) &&
transparent_hugepage_use_zero_page()) {
spinlock_t *ptl;
pgtable_t pgtable;
struct page *zero_page;
bool set;
pgtable = pte_alloc_one(mm, haddr);
if (unlikely(!pgtable))
return VM_FAULT_OOM;
zero_page = get_huge_zero_page();
if (unlikely(!zero_page)) {
pte_free(mm, pgtable);
count_vm_event(THP_FAULT_FALLBACK);
return VM_FAULT_FALLBACK;
}
ptl = pmd_lock(mm, pmd);
set = set_huge_zero_page(pgtable, mm, vma, haddr, pmd,
zero_page);
spin_unlock(ptl);
if (!set) {
pte_free(mm, pgtable);
put_huge_zero_page();
}
return 0;
}
gfp = alloc_hugepage_gfpmask(transparent_hugepage_defrag(vma), 0);
page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER);
if (unlikely(!page)) {
count_vm_event(THP_FAULT_FALLBACK);
return VM_FAULT_FALLBACK;
}
if (unlikely(__do_huge_pmd_anonymous_page(mm, vma, haddr, pmd, page, gfp))) {
put_page(page);
count_vm_event(THP_FAULT_FALLBACK);
return VM_FAULT_FALLBACK;
}
count_vm_event(THP_FAULT_ALLOC);
return 0;
}
int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
struct vm_area_struct *vma)
{
spinlock_t *dst_ptl, *src_ptl;
struct page *src_page;
pmd_t pmd;
pgtable_t pgtable;
int ret;
ret = -ENOMEM;
pgtable = pte_alloc_one(dst_mm, addr);
if (unlikely(!pgtable))
goto out;
dst_ptl = pmd_lock(dst_mm, dst_pmd);
src_ptl = pmd_lockptr(src_mm, src_pmd);
spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
ret = -EAGAIN;
pmd = *src_pmd;
if (unlikely(!pmd_trans_huge(pmd))) {
pte_free(dst_mm, pgtable);
goto out_unlock;
}
/*
* When page table lock is held, the huge zero pmd should not be
* under splitting since we don't split the page itself, only pmd to
* a page table.
*/
if (is_huge_zero_pmd(pmd)) {
struct page *zero_page;
bool set;
/*
* get_huge_zero_page() will never allocate a new page here,
* since we already have a zero page to copy. It just takes a
* reference.
*/
zero_page = get_huge_zero_page();
set = set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
zero_page);
BUG_ON(!set); /* unexpected !pmd_none(dst_pmd) */
ret = 0;
goto out_unlock;
}
if (unlikely(pmd_trans_splitting(pmd))) {
/* split huge page running from under us */
spin_unlock(src_ptl);
spin_unlock(dst_ptl);
pte_free(dst_mm, pgtable);
wait_split_huge_page(vma->anon_vma, src_pmd); /* src_vma */
goto out;
}
src_page = pmd_page(pmd);
VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
get_page(src_page);
page_dup_rmap(src_page);
add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
pmdp_set_wrprotect(src_mm, addr, src_pmd);
pmd = pmd_mkold(pmd_wrprotect(pmd));
pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
set_pmd_at(dst_mm, addr, dst_pmd, pmd);
atomic_long_inc(&dst_mm->nr_ptes);
ret = 0;
out_unlock:
spin_unlock(src_ptl);
spin_unlock(dst_ptl);
out:
return ret;
}
void huge_pmd_set_accessed(struct mm_struct *mm,
struct vm_area_struct *vma,
unsigned long address,
pmd_t *pmd, pmd_t orig_pmd,
int dirty)
{
spinlock_t *ptl;
pmd_t entry;
unsigned long haddr;
ptl = pmd_lock(mm, pmd);
if (unlikely(!pmd_same(*pmd, orig_pmd)))
goto unlock;
entry = pmd_mkyoung(orig_pmd);
haddr = address & HPAGE_PMD_MASK;
if (pmdp_set_access_flags(vma, haddr, pmd, entry, dirty))
update_mmu_cache_pmd(vma, address, pmd);
unlock:
spin_unlock(ptl);
}
/*
* Save CONFIG_DEBUG_PAGEALLOC from faulting falsely on tail pages
* during copy_user_huge_page()'s copy_page_rep(): in the case when
* the source page gets split and a tail freed before copy completes.
* Called under pmd_lock of checked pmd, so safe from splitting itself.
*/
static void get_user_huge_page(struct page *page)
{
if (IS_ENABLED(CONFIG_DEBUG_PAGEALLOC)) {
struct page *endpage = page + HPAGE_PMD_NR;
atomic_add(HPAGE_PMD_NR, &page->_count);
while (++page < endpage)
get_huge_page_tail(page);
} else {
get_page(page);
}
}
static void put_user_huge_page(struct page *page)
{
if (IS_ENABLED(CONFIG_DEBUG_PAGEALLOC)) {
struct page *endpage = page + HPAGE_PMD_NR;
while (page < endpage)
put_page(page++);
} else {
put_page(page);
}
}
static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm,
struct vm_area_struct *vma,
unsigned long address,
pmd_t *pmd, pmd_t orig_pmd,
struct page *page,
unsigned long haddr)
{
struct mem_cgroup *memcg;
spinlock_t *ptl;
pgtable_t pgtable;
pmd_t _pmd;
int ret = 0, i;
struct page **pages;
unsigned long mmun_start; /* For mmu_notifiers */
unsigned long mmun_end; /* For mmu_notifiers */
pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR,
GFP_KERNEL);
if (unlikely(!pages)) {
ret |= VM_FAULT_OOM;
goto out;
}
for (i = 0; i < HPAGE_PMD_NR; i++) {
pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE |
__GFP_OTHER_NODE,
vma, address, page_to_nid(page));
if (unlikely(!pages[i] ||
mem_cgroup_try_charge(pages[i], mm, GFP_KERNEL,
&memcg))) {
if (pages[i])
put_page(pages[i]);
while (--i >= 0) {
memcg = (void *)page_private(pages[i]);
set_page_private(pages[i], 0);
mem_cgroup_cancel_charge(pages[i], memcg);
put_page(pages[i]);
}
kfree(pages);
ret |= VM_FAULT_OOM;
goto out;
}
set_page_private(pages[i], (unsigned long)memcg);
}
for (i = 0; i < HPAGE_PMD_NR; i++) {
copy_user_highpage(pages[i], page + i,
haddr + PAGE_SIZE * i, vma);
__SetPageUptodate(pages[i]);
cond_resched();
}
mmun_start = haddr;
mmun_end = haddr + HPAGE_PMD_SIZE;
mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
ptl = pmd_lock(mm, pmd);
if (unlikely(!pmd_same(*pmd, orig_pmd)))
goto out_free_pages;
VM_BUG_ON_PAGE(!PageHead(page), page);
pmdp_clear_flush_notify(vma, haddr, pmd);
/* leave pmd empty until pte is filled */
pgtable = pgtable_trans_huge_withdraw(mm, pmd);
pmd_populate(mm, &_pmd, pgtable);
for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
pte_t *pte, entry;
entry = mk_pte(pages[i], vma->vm_page_prot);
entry = maybe_mkwrite(pte_mkdirty(entry), vma);
memcg = (void *)page_private(pages[i]);
set_page_private(pages[i], 0);
page_add_new_anon_rmap(pages[i], vma, haddr);
mem_cgroup_commit_charge(pages[i], memcg, false);
lru_cache_add_active_or_unevictable(pages[i], vma);
pte = pte_offset_map(&_pmd, haddr);
VM_BUG_ON(!pte_none(*pte));
set_pte_at(mm, haddr, pte, entry);
pte_unmap(pte);
}
kfree(pages);
smp_wmb(); /* make pte visible before pmd */
pmd_populate(mm, pmd, pgtable);
page_remove_rmap(page);
spin_unlock(ptl);
mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
ret |= VM_FAULT_WRITE;
put_page(page);
out:
return ret;
out_free_pages:
spin_unlock(ptl);
mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
for (i = 0; i < HPAGE_PMD_NR; i++) {
memcg = (void *)page_private(pages[i]);
set_page_private(pages[i], 0);
mem_cgroup_cancel_charge(pages[i], memcg);
put_page(pages[i]);
}
kfree(pages);
goto out;
}
int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
unsigned long address, pmd_t *pmd, pmd_t orig_pmd)
{
spinlock_t *ptl;
int ret = 0;
struct page *page = NULL, *new_page;
struct mem_cgroup *memcg;
unsigned long haddr;
unsigned long mmun_start; /* For mmu_notifiers */
unsigned long mmun_end; /* For mmu_notifiers */
gfp_t huge_gfp; /* for allocation and charge */
ptl = pmd_lockptr(mm, pmd);
VM_BUG_ON_VMA(!vma->anon_vma, vma);
haddr = address & HPAGE_PMD_MASK;
if (is_huge_zero_pmd(orig_pmd))
goto alloc;
spin_lock(ptl);
if (unlikely(!pmd_same(*pmd, orig_pmd)))
goto out_unlock;
page = pmd_page(orig_pmd);
VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page);
if (page_mapcount(page) == 1) {
pmd_t entry;
entry = pmd_mkyoung(orig_pmd);
entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
if (pmdp_set_access_flags(vma, haddr, pmd, entry, 1))
update_mmu_cache_pmd(vma, address, pmd);
ret |= VM_FAULT_WRITE;
goto out_unlock;
}
get_user_huge_page(page);
spin_unlock(ptl);
alloc:
if (transparent_hugepage_enabled(vma) &&
!transparent_hugepage_debug_cow()) {
huge_gfp = alloc_hugepage_gfpmask(transparent_hugepage_defrag(vma), 0);
new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER);
} else
new_page = NULL;
if (unlikely(!new_page)) {
if (!page) {
split_huge_page_pmd(vma, address, pmd);
ret |= VM_FAULT_FALLBACK;
} else {
ret = do_huge_pmd_wp_page_fallback(mm, vma, address,
pmd, orig_pmd, page, haddr);
if (ret & VM_FAULT_OOM) {
split_huge_page(page);
ret |= VM_FAULT_FALLBACK;
}
put_user_huge_page(page);
}
count_vm_event(THP_FAULT_FALLBACK);
goto out;
}
if (unlikely(mem_cgroup_try_charge(new_page, mm, huge_gfp, &memcg))) {
put_page(new_page);
if (page) {
split_huge_page(page);
put_user_huge_page(page);
} else
split_huge_page_pmd(vma, address, pmd);
ret |= VM_FAULT_FALLBACK;
count_vm_event(THP_FAULT_FALLBACK);
goto out;
}
count_vm_event(THP_FAULT_ALLOC);
if (!page)
clear_huge_page(new_page, haddr, HPAGE_PMD_NR);
else
copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR);
__SetPageUptodate(new_page);
mmun_start = haddr;
mmun_end = haddr + HPAGE_PMD_SIZE;
mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
spin_lock(ptl);
if (page)
put_user_huge_page(page);
if (unlikely(!pmd_same(*pmd, orig_pmd))) {
spin_unlock(ptl);
mem_cgroup_cancel_charge(new_page, memcg);
put_page(new_page);
goto out_mn;
} else {
pmd_t entry;
entry = mk_huge_pmd(new_page, vma->vm_page_prot);
entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
pmdp_clear_flush_notify(vma, haddr, pmd);
page_add_new_anon_rmap(new_page, vma, haddr);
mem_cgroup_commit_charge(new_page, memcg, false);
lru_cache_add_active_or_unevictable(new_page, vma);
set_pmd_at(mm, haddr, pmd, entry);
update_mmu_cache_pmd(vma, address, pmd);
if (!page) {
add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
put_huge_zero_page();
} else {
VM_BUG_ON_PAGE(!PageHead(page), page);
page_remove_rmap(page);
put_page(page);
}
ret |= VM_FAULT_WRITE;
}
spin_unlock(ptl);
out_mn:
mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
out:
return ret;
out_unlock:
spin_unlock(ptl);
return ret;
}
struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
unsigned long addr,
pmd_t *pmd,
unsigned int flags)
{
struct mm_struct *mm = vma->vm_mm;
struct page *page = NULL;
assert_spin_locked(pmd_lockptr(mm, pmd));
if (flags & FOLL_WRITE && !pmd_write(*pmd))
goto out;
/* Avoid dumping huge zero page */
if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
return ERR_PTR(-EFAULT);
/* Full NUMA hinting faults to serialise migration in fault paths */
if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
goto out;
page = pmd_page(*pmd);
VM_BUG_ON_PAGE(!PageHead(page), page);
if (flags & FOLL_TOUCH) {
pmd_t _pmd;
/*
* We should set the dirty bit only for FOLL_WRITE but
* for now the dirty bit in the pmd is meaningless.
* And if the dirty bit will become meaningful and
* we'll only set it with FOLL_WRITE, an atomic
* set_bit will be required on the pmd to set the
* young bit, instead of the current set_pmd_at.
*/
_pmd = pmd_mkyoung(pmd_mkdirty(*pmd));
if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
pmd, _pmd, 1))
update_mmu_cache_pmd(vma, addr, pmd);
}
if ((flags & FOLL_POPULATE) && (vma->vm_flags & VM_LOCKED)) {
if (page->mapping && trylock_page(page)) {
lru_add_drain();
if (page->mapping)
mlock_vma_page(page);
unlock_page(page);
}
}
page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
VM_BUG_ON_PAGE(!PageCompound(page), page);
if (flags & FOLL_GET)
get_page_foll(page);
out:
return page;
}
/* NUMA hinting page fault entry point for trans huge pmds */
int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
unsigned long addr, pmd_t pmd, pmd_t *pmdp)
{
spinlock_t *ptl;
struct anon_vma *anon_vma = NULL;
struct page *page;
unsigned long haddr = addr & HPAGE_PMD_MASK;
int page_nid = -1, this_nid = numa_node_id();
int target_nid, last_cpupid = -1;
bool page_locked;
bool migrated = false;
bool was_writable;
int flags = 0;
/* A PROT_NONE fault should not end up here */
BUG_ON(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)));
ptl = pmd_lock(mm, pmdp);
if (unlikely(!pmd_same(pmd, *pmdp)))
goto out_unlock;
/*
* If there are potential migrations, wait for completion and retry
* without disrupting NUMA hinting information. Do not relock and
* check_same as the page may no longer be mapped.
*/
if (unlikely(pmd_trans_migrating(*pmdp))) {
page = pmd_page(*pmdp);
spin_unlock(ptl);
wait_on_page_locked(page);
goto out;
}
page = pmd_page(pmd);
BUG_ON(is_huge_zero_page(page));
page_nid = page_to_nid(page);
last_cpupid = page_cpupid_last(page);
count_vm_numa_event(NUMA_HINT_FAULTS);
if (page_nid == this_nid) {
count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
flags |= TNF_FAULT_LOCAL;
}
/* See similar comment in do_numa_page for explanation */
if (!(vma->vm_flags & VM_WRITE))
flags |= TNF_NO_GROUP;
/*
* Acquire the page lock to serialise THP migrations but avoid dropping
* page_table_lock if at all possible
*/
page_locked = trylock_page(page);
target_nid = mpol_misplaced(page, vma, haddr);
if (target_nid == -1) {
/* If the page was locked, there are no parallel migrations */
if (page_locked)
goto clear_pmdnuma;
}
/* Migration could have started since the pmd_trans_migrating check */
if (!page_locked) {
spin_unlock(ptl);
wait_on_page_locked(page);
page_nid = -1;
goto out;
}
/*
* Page is misplaced. Page lock serialises migrations. Acquire anon_vma
* to serialises splits
*/
get_page(page);
spin_unlock(ptl);
anon_vma = page_lock_anon_vma_read(page);
/* Confirm the PMD did not change while page_table_lock was released */
spin_lock(ptl);
if (unlikely(!pmd_same(pmd, *pmdp))) {
unlock_page(page);
put_page(page);
page_nid = -1;
goto out_unlock;
}
/* Bail if we fail to protect against THP splits for any reason */
if (unlikely(!anon_vma)) {
put_page(page);
page_nid = -1;
goto clear_pmdnuma;
}
/*
* Migrate the THP to the requested node, returns with page unlocked
* and access rights restored.
*/
spin_unlock(ptl);
migrated = migrate_misplaced_transhuge_page(mm, vma,
pmdp, pmd, addr, page, target_nid);
if (migrated) {
flags |= TNF_MIGRATED;
page_nid = target_nid;
} else
flags |= TNF_MIGRATE_FAIL;
goto out;
clear_pmdnuma:
BUG_ON(!PageLocked(page));
was_writable = pmd_write(pmd);
pmd = pmd_modify(pmd, vma->vm_page_prot);
pmd = pmd_mkyoung(pmd);
if (was_writable)
pmd = pmd_mkwrite(pmd);
set_pmd_at(mm, haddr, pmdp, pmd);
update_mmu_cache_pmd(vma, addr, pmdp);
unlock_page(page);
out_unlock:
spin_unlock(ptl);
out:
if (anon_vma)
page_unlock_anon_vma_read(anon_vma);
if (page_nid != -1)
task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR, flags);
return 0;
}
int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
pmd_t *pmd, unsigned long addr)
{
spinlock_t *ptl;
int ret = 0;
if (__pmd_trans_huge_lock(pmd, vma, &ptl) == 1) {
struct page *page;
pgtable_t pgtable;
pmd_t orig_pmd;
/*
* For architectures like ppc64 we look at deposited pgtable
* when calling pmdp_get_and_clear. So do the
* pgtable_trans_huge_withdraw after finishing pmdp related
* operations.
*/
orig_pmd = pmdp_get_and_clear_full(tlb->mm, addr, pmd,
tlb->fullmm);
tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
pgtable = pgtable_trans_huge_withdraw(tlb->mm, pmd);
if (is_huge_zero_pmd(orig_pmd)) {
atomic_long_dec(&tlb->mm->nr_ptes);
spin_unlock(ptl);
put_huge_zero_page();
} else {
page = pmd_page(orig_pmd);
page_remove_rmap(page);
VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
VM_BUG_ON_PAGE(!PageHead(page), page);
atomic_long_dec(&tlb->mm->nr_ptes);
spin_unlock(ptl);
tlb_remove_page(tlb, page);
}
pte_free(tlb->mm, pgtable);
ret = 1;
}
return ret;
}
int move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma,
unsigned long old_addr,
unsigned long new_addr, unsigned long old_end,
pmd_t *old_pmd, pmd_t *new_pmd)
{
spinlock_t *old_ptl, *new_ptl;
int ret = 0;
pmd_t pmd;
struct mm_struct *mm = vma->vm_mm;
if ((old_addr & ~HPAGE_PMD_MASK) ||
(new_addr & ~HPAGE_PMD_MASK) ||
old_end - old_addr < HPAGE_PMD_SIZE ||
(new_vma->vm_flags & VM_NOHUGEPAGE))
goto out;
/*
* The destination pmd shouldn't be established, free_pgtables()
* should have release it.
*/
if (WARN_ON(!pmd_none(*new_pmd))) {
VM_BUG_ON(pmd_trans_huge(*new_pmd));
goto out;
}
/*
* We don't have to worry about the ordering of src and dst
* ptlocks because exclusive mmap_sem prevents deadlock.
*/
ret = __pmd_trans_huge_lock(old_pmd, vma, &old_ptl);
if (ret == 1) {
new_ptl = pmd_lockptr(mm, new_pmd);
if (new_ptl != old_ptl)
spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
pmd = pmdp_get_and_clear(mm, old_addr, old_pmd);
VM_BUG_ON(!pmd_none(*new_pmd));
if (pmd_move_must_withdraw(new_ptl, old_ptl)) {
pgtable_t pgtable;
pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
}
set_pmd_at(mm, new_addr, new_pmd, pmd_mksoft_dirty(pmd));
if (new_ptl != old_ptl)
spin_unlock(new_ptl);
spin_unlock(old_ptl);
}
out:
return ret;
}
/*
* Returns
* - 0 if PMD could not be locked
* - 1 if PMD was locked but protections unchange and TLB flush unnecessary
* - HPAGE_PMD_NR is protections changed and TLB flush necessary
*/
int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
unsigned long addr, pgprot_t newprot, int prot_numa)
{
struct mm_struct *mm = vma->vm_mm;
spinlock_t *ptl;
int ret = 0;
if (__pmd_trans_huge_lock(pmd, vma, &ptl) == 1) {
pmd_t entry;
bool preserve_write = prot_numa && pmd_write(*pmd);
ret = 1;
/*
* Avoid trapping faults against the zero page. The read-only
* data is likely to be read-cached on the local CPU and
* local/remote hits to the zero page are not interesting.
*/
if (prot_numa && is_huge_zero_pmd(*pmd)) {
spin_unlock(ptl);
return ret;
}
if (!prot_numa || !pmd_protnone(*pmd)) {
entry = pmdp_get_and_clear_notify(mm, addr, pmd);
entry = pmd_modify(entry, newprot);
if (preserve_write)
entry = pmd_mkwrite(entry);
ret = HPAGE_PMD_NR;
set_pmd_at(mm, addr, pmd, entry);
BUG_ON(!preserve_write && pmd_write(entry));
}
spin_unlock(ptl);
}
return ret;
}
/*
* Returns 1 if a given pmd maps a stable (not under splitting) thp.
* Returns -1 if it maps a thp under splitting. Returns 0 otherwise.
*
* Note that if it returns 1, this routine returns without unlocking page
* table locks. So callers must unlock them.
*/
int __pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma,
spinlock_t **ptl)
{
*ptl = pmd_lock(vma->vm_mm, pmd);
if (likely(pmd_trans_huge(*pmd))) {
if (unlikely(pmd_trans_splitting(*pmd))) {
spin_unlock(*ptl);
wait_split_huge_page(vma->anon_vma, pmd);
return -1;
} else {
/* Thp mapped by 'pmd' is stable, so we can
* handle it as it is. */
return 1;
}
}
spin_unlock(*ptl);
return 0;
}
/*
* This function returns whether a given @page is mapped onto the @address
* in the virtual space of @mm.
*
* When it's true, this function returns *pmd with holding the page table lock
* and passing it back to the caller via @ptl.
* If it's false, returns NULL without holding the page table lock.
*/
pmd_t *page_check_address_pmd(struct page *page,
struct mm_struct *mm,
unsigned long address,
enum page_check_address_pmd_flag flag,
spinlock_t **ptl)
{
pgd_t *pgd;
pud_t *pud;
pmd_t *pmd;
if (address & ~HPAGE_PMD_MASK)
return NULL;
pgd = pgd_offset(mm, address);
if (!pgd_present(*pgd))
return NULL;
pud = pud_offset(pgd, address);
if (!pud_present(*pud))
return NULL;
pmd = pmd_offset(pud, address);
*ptl = pmd_lock(mm, pmd);
if (!pmd_present(*pmd))
goto unlock;
if (pmd_page(*pmd) != page)
goto unlock;
/*
* split_vma() may create temporary aliased mappings. There is
* no risk as long as all huge pmd are found and have their
* splitting bit set before __split_huge_page_refcount
* runs. Finding the same huge pmd more than once during the
* same rmap walk is not a problem.
*/
if (flag == PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG &&
pmd_trans_splitting(*pmd))
goto unlock;
if (pmd_trans_huge(*pmd)) {
VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG &&
!pmd_trans_splitting(*pmd));
return pmd;
}
unlock:
spin_unlock(*ptl);
return NULL;
}
static int __split_huge_page_splitting(struct page *page,
struct vm_area_struct *vma,
unsigned long address)
{
struct mm_struct *mm = vma->vm_mm;
spinlock_t *ptl;
pmd_t *pmd;
int ret = 0;
/* For mmu_notifiers */
const unsigned long mmun_start = address;
const unsigned long mmun_end = address + HPAGE_PMD_SIZE;
mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
pmd = page_check_address_pmd(page, mm, address,
PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG, &ptl);
if (pmd) {
/*
* We can't temporarily set the pmd to null in order
* to split it, the pmd must remain marked huge at all
* times or the VM won't take the pmd_trans_huge paths
* and it won't wait on the anon_vma->root->rwsem to
* serialize against split_huge_page*.
*/
pmdp_splitting_flush(vma, address, pmd);
ret = 1;
spin_unlock(ptl);
}
mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
return ret;
}
static void __split_huge_page_refcount(struct page *page,
struct list_head *list)
{
int i;
struct zone *zone = page_zone(page);
struct lruvec *lruvec;
int tail_count = 0;
/* prevent PageLRU to go away from under us, and freeze lru stats */
spin_lock_irq(&zone->lru_lock);
lruvec = mem_cgroup_page_lruvec(page, zone);
compound_lock(page);
/* complete memcg works before add pages to LRU */
mem_cgroup_split_huge_fixup(page);
for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
struct page *page_tail = page + i;
/* tail_page->_mapcount cannot change */
BUG_ON(page_mapcount(page_tail) < 0);
tail_count += page_mapcount(page_tail);
/* check for overflow */
BUG_ON(tail_count < 0);
BUG_ON(atomic_read(&page_tail->_count) != 0);
/*
* tail_page->_count is zero and not changing from
* under us. But get_page_unless_zero() may be running
* from under us on the tail_page. If we used
* atomic_set() below instead of atomic_add(), we
* would then run atomic_set() concurrently with
* get_page_unless_zero(), and atomic_set() is
* implemented in C not using locked ops. spin_unlock
* on x86 sometime uses locked ops because of PPro
* errata 66, 92, so unless somebody can guarantee
* atomic_set() here would be safe on all archs (and
* not only on x86), it's safer to use atomic_add().
*/
atomic_add(page_mapcount(page) + page_mapcount(page_tail) + 1,
&page_tail->_count);
/* after clearing PageTail the gup refcount can be released */
smp_mb__after_atomic();
/*
* retain hwpoison flag of the poisoned tail page:
* fix for the unsuitable process killed on Guest Machine(KVM)
* by the memory-failure.
*/
page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP | __PG_HWPOISON;
page_tail->flags |= (page->flags &
((1L << PG_referenced) |
(1L << PG_swapbacked) |
(1L << PG_mlocked) |
(1L << PG_uptodate) |
(1L << PG_active) |
(1L << PG_unevictable)));
page_tail->flags |= (1L << PG_dirty);
/* clear PageTail before overwriting first_page */
smp_wmb();
/*
* __split_huge_page_splitting() already set the
* splitting bit in all pmd that could map this
* hugepage, that will ensure no CPU can alter the
* mapcount on the head page. The mapcount is only
* accounted in the head page and it has to be
* transferred to all tail pages in the below code. So
* for this code to be safe, the split the mapcount
* can't change. But that doesn't mean userland can't
* keep changing and reading the page contents while
* we transfer the mapcount, so the pmd splitting
* status is achieved setting a reserved bit in the
* pmd, not by clearing the present bit.
*/
page_tail->_mapcount = page->_mapcount;
BUG_ON(page_tail->mapping);
page_tail->mapping = page->mapping;
page_tail->index = page->index + i;
page_cpupid_xchg_last(page_tail, page_cpupid_last(page));
BUG_ON(!PageAnon(page_tail));
BUG_ON(!PageUptodate(page_tail));
BUG_ON(!PageDirty(page_tail));
BUG_ON(!PageSwapBacked(page_tail));
lru_add_page_tail(page, page_tail, lruvec, list);
}
atomic_sub(tail_count, &page->_count);
BUG_ON(atomic_read(&page->_count) <= 0);
__mod_zone_page_state(zone, NR_ANON_TRANSPARENT_HUGEPAGES, -1);
ClearPageCompound(page);
compound_unlock(page);
spin_unlock_irq(&zone->lru_lock);
for (i = 1; i < HPAGE_PMD_NR; i++) {
struct page *page_tail = page + i;
BUG_ON(page_count(page_tail) <= 0);
/*
* Tail pages may be freed if there wasn't any mapping
* like if add_to_swap() is running on a lru page that
* had its mapping zapped. And freeing these pages
* requires taking the lru_lock so we do the put_page
* of the tail pages after the split is complete.
*/
put_page(page_tail);
}
/*
* Only the head page (now become a regular page) is required
* to be pinned by the caller.
*/
BUG_ON(page_count(page) <= 0);
}
static int __split_huge_page_map(struct page *page,
struct vm_area_struct *vma,
unsigned long address)
{
struct mm_struct *mm = vma->vm_mm;
spinlock_t *ptl;
pmd_t *pmd, _pmd;
int ret = 0, i;
pgtable_t pgtable;
unsigned long haddr;
pmd = page_check_address_pmd(page, mm, address,
PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG, &ptl);
if (pmd) {
pgtable = pgtable_trans_huge_withdraw(mm, pmd);
pmd_populate(mm, &_pmd, pgtable);
if (pmd_write(*pmd))
BUG_ON(page_mapcount(page) != 1);
haddr = address;
for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
pte_t *pte, entry;
BUG_ON(PageCompound(page+i));
/*
* Note that NUMA hinting access restrictions are not
* transferred to avoid any possibility of altering
* permissions across VMAs.
*/
entry = mk_pte(page + i, vma->vm_page_prot);
entry = maybe_mkwrite(pte_mkdirty(entry), vma);
if (!pmd_write(*pmd))
entry = pte_wrprotect(entry);
if (!pmd_young(*pmd))
entry = pte_mkold(entry);
pte = pte_offset_map(&_pmd, haddr);
BUG_ON(!pte_none(*pte));
set_pte_at(mm, haddr, pte, entry);
pte_unmap(pte);
}
smp_wmb(); /* make pte visible before pmd */
/*
* Up to this point the pmd is present and huge and
* userland has the whole access to the hugepage
* during the split (which happens in place). If we
* overwrite the pmd with the not-huge version
* pointing to the pte here (which of course we could
* if all CPUs were bug free), userland could trigger
* a small page size TLB miss on the small sized TLB
* while the hugepage TLB entry is still established
* in the huge TLB. Some CPU doesn't like that. See
* http://support.amd.com/us/Processor_TechDocs/41322.pdf,
* Erratum 383 on page 93. Intel should be safe but is
* also warns that it's only safe if the permission
* and cache attributes of the two entries loaded in
* the two TLB is identical (which should be the case
* here). But it is generally safer to never allow
* small and huge TLB entries for the same virtual
* address to be loaded simultaneously. So instead of
* doing "pmd_populate(); flush_tlb_range();" we first
* mark the current pmd notpresent (atomically because
* here the pmd_trans_huge and pmd_trans_splitting
* must remain set at all times on the pmd until the
* split is complete for this pmd), then we flush the
* SMP TLB and finally we write the non-huge version
* of the pmd entry with pmd_populate.
*/
pmdp_invalidate(vma, address, pmd);
pmd_populate(mm, pmd, pgtable);
ret = 1;
spin_unlock(ptl);
}
return ret;
}
/* must be called with anon_vma->root->rwsem held */
static void __split_huge_page(struct page *page,
struct anon_vma *anon_vma,
struct list_head *list)
{
int mapcount, mapcount2;
pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
struct anon_vma_chain *avc;
BUG_ON(!PageHead(page));
BUG_ON(PageTail(page));
mapcount = 0;
anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
struct vm_area_struct *vma = avc->vma;
unsigned long addr = vma_address(page, vma);
BUG_ON(is_vma_temporary_stack(vma));
mapcount += __split_huge_page_splitting(page, vma, addr);
}
/*
* It is critical that new vmas are added to the tail of the
* anon_vma list. This guarantes that if copy_huge_pmd() runs
* and establishes a child pmd before
* __split_huge_page_splitting() freezes the parent pmd (so if
* we fail to prevent copy_huge_pmd() from running until the
* whole __split_huge_page() is complete), we will still see
* the newly established pmd of the child later during the
* walk, to be able to set it as pmd_trans_splitting too.
*/
if (mapcount != page_mapcount(page)) {
pr_err("mapcount %d page_mapcount %d\n",
mapcount, page_mapcount(page));
BUG();
}
__split_huge_page_refcount(page, list);
mapcount2 = 0;
anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
struct vm_area_struct *vma = avc->vma;
unsigned long addr = vma_address(page, vma);
BUG_ON(is_vma_temporary_stack(vma));
mapcount2 += __split_huge_page_map(page, vma, addr);
}
if (mapcount != mapcount2) {
pr_err("mapcount %d mapcount2 %d page_mapcount %d\n",
mapcount, mapcount2, page_mapcount(page));
BUG();
}
}
/*
* Split a hugepage into normal pages. This doesn't change the position of head
* page. If @list is null, tail pages will be added to LRU list, otherwise, to
* @list. Both head page and tail pages will inherit mapping, flags, and so on
* from the hugepage.
* Return 0 if the hugepage is split successfully otherwise return 1.
*/
int split_huge_page_to_list(struct page *page, struct list_head *list)
{
struct anon_vma *anon_vma;
int ret = 1;
BUG_ON(is_huge_zero_page(page));
BUG_ON(!PageAnon(page));
/*
* The caller does not necessarily hold an mmap_sem that would prevent
* the anon_vma disappearing so we first we take a reference to it
* and then lock the anon_vma for write. This is similar to
* page_lock_anon_vma_read except the write lock is taken to serialise
* against parallel split or collapse operations.
*/
anon_vma = page_get_anon_vma(page);
if (!anon_vma)
goto out;
anon_vma_lock_write(anon_vma);
ret = 0;
if (!PageCompound(page))
goto out_unlock;
BUG_ON(!PageSwapBacked(page));
__split_huge_page(page, anon_vma, list);
count_vm_event(THP_SPLIT);
BUG_ON(PageCompound(page));
out_unlock:
anon_vma_unlock_write(anon_vma);
put_anon_vma(anon_vma);
out:
return ret;
}
#define VM_NO_THP (VM_SPECIAL | VM_HUGETLB | VM_SHARED | VM_MAYSHARE)
int hugepage_madvise(struct vm_area_struct *vma,
unsigned long *vm_flags, int advice)
{
switch (advice) {
case MADV_HUGEPAGE:
#ifdef CONFIG_S390
/*
* qemu blindly sets MADV_HUGEPAGE on all allocations, but s390
* can't handle this properly after s390_enable_sie, so we simply
* ignore the madvise to prevent qemu from causing a SIGSEGV.
*/
if (mm_has_pgste(vma->vm_mm))
return 0;
#endif
/*
* Be somewhat over-protective like KSM for now!
*/
if (*vm_flags & (VM_HUGEPAGE | VM_NO_THP))
return -EINVAL;
*vm_flags &= ~VM_NOHUGEPAGE;
*vm_flags |= VM_HUGEPAGE;
/*
* If the vma become good for khugepaged to scan,
* register it here without waiting a page fault that
* may not happen any time soon.
*/
if (unlikely(khugepaged_enter_vma_merge(vma, *vm_flags)))
return -ENOMEM;
break;
case MADV_NOHUGEPAGE:
/*
* Be somewhat over-protective like KSM for now!
*/
if (*vm_flags & (VM_NOHUGEPAGE | VM_NO_THP))
return -EINVAL;
*vm_flags &= ~VM_HUGEPAGE;
*vm_flags |= VM_NOHUGEPAGE;
/*
* Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
* this vma even if we leave the mm registered in khugepaged if
* it got registered before VM_NOHUGEPAGE was set.
*/
break;
}
return 0;
}
static int __init khugepaged_slab_init(void)
{
mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
sizeof(struct mm_slot),
__alignof__(struct mm_slot), 0, NULL);
if (!mm_slot_cache)
return -ENOMEM;
return 0;
}
static void __init khugepaged_slab_exit(void)
{
kmem_cache_destroy(mm_slot_cache);
}
static inline struct mm_slot *alloc_mm_slot(void)
{
if (!mm_slot_cache) /* initialization failed */
return NULL;
return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
}
static inline void free_mm_slot(struct mm_slot *mm_slot)
{
kmem_cache_free(mm_slot_cache, mm_slot);
}
static struct mm_slot *get_mm_slot(struct mm_struct *mm)
{
struct mm_slot *mm_slot;
hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm)
if (mm == mm_slot->mm)
return mm_slot;
return NULL;
}
static void insert_to_mm_slots_hash(struct mm_struct *mm,
struct mm_slot *mm_slot)
{
mm_slot->mm = mm;
hash_add(mm_slots_hash, &mm_slot->hash, (long)mm);
}
static inline int khugepaged_test_exit(struct mm_struct *mm)
{
return atomic_read(&mm->mm_users) == 0;
}
int __khugepaged_enter(struct mm_struct *mm)
{
struct mm_slot *mm_slot;
int wakeup;
mm_slot = alloc_mm_slot();
if (!mm_slot)
return -ENOMEM;
/* __khugepaged_exit() must not run from under us */
VM_BUG_ON_MM(khugepaged_test_exit(mm), mm);
if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
free_mm_slot(mm_slot);
return 0;
}
spin_lock(&khugepaged_mm_lock);
insert_to_mm_slots_hash(mm, mm_slot);
/*
* Insert just behind the scanning cursor, to let the area settle
* down a little.
*/
wakeup = list_empty(&khugepaged_scan.mm_head);
list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
spin_unlock(&khugepaged_mm_lock);
atomic_inc(&mm->mm_count);
if (wakeup)
wake_up_interruptible(&khugepaged_wait);
return 0;
}
int khugepaged_enter_vma_merge(struct vm_area_struct *vma,
unsigned long vm_flags)
{
unsigned long hstart, hend;
if (!vma->anon_vma)
/*
* Not yet faulted in so we will register later in the
* page fault if needed.
*/
return 0;
if (vma->vm_ops)
/* khugepaged not yet working on file or special mappings */
return 0;
VM_BUG_ON_VMA(vm_flags & VM_NO_THP, vma);
hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
hend = vma->vm_end & HPAGE_PMD_MASK;
if (hstart < hend)
return khugepaged_enter(vma, vm_flags);
return 0;
}
void __khugepaged_exit(struct mm_struct *mm)
{
struct mm_slot *mm_slot;
int free = 0;
spin_lock(&khugepaged_mm_lock);
mm_slot = get_mm_slot(mm);
if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
hash_del(&mm_slot->hash);
list_del(&mm_slot->mm_node);
free = 1;
}
spin_unlock(&khugepaged_mm_lock);
if (free) {
clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
free_mm_slot(mm_slot);
mmdrop(mm);
} else if (mm_slot) {
/*
* This is required to serialize against
* khugepaged_test_exit() (which is guaranteed to run
* under mmap sem read mode). Stop here (after we
* return all pagetables will be destroyed) until
* khugepaged has finished working on the pagetables
* under the mmap_sem.
*/
down_write(&mm->mmap_sem);
up_write(&mm->mmap_sem);
}
}
static void release_pte_page(struct page *page)
{
/* 0 stands for page_is_file_cache(page) == false */
dec_zone_page_state(page, NR_ISOLATED_ANON + 0);
unlock_page(page);
putback_lru_page(page);
}
static void release_pte_pages(pte_t *pte, pte_t *_pte)
{
while (--_pte >= pte) {
pte_t pteval = *_pte;
if (!pte_none(pteval) && !is_zero_pfn(pte_pfn(pteval)))
release_pte_page(pte_page(pteval));
}
}
static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
unsigned long address,
pte_t *pte)
{
struct page *page;
pte_t *_pte;
int none_or_zero = 0;
bool referenced = false, writable = false;
for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
_pte++, address += PAGE_SIZE) {
pte_t pteval = *_pte;
if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
if (++none_or_zero <= khugepaged_max_ptes_none)
continue;
else
goto out;
}
if (!pte_present(pteval))
goto out;
page = vm_normal_page(vma, address, pteval);
if (unlikely(!page))
goto out;
VM_BUG_ON_PAGE(PageCompound(page), page);
VM_BUG_ON_PAGE(!PageAnon(page), page);
VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
/*
* We can do it before isolate_lru_page because the
* page can't be freed from under us. NOTE: PG_lock
* is needed to serialize against split_huge_page
* when invoked from the VM.
*/
if (!trylock_page(page))
goto out;
/*
* cannot use mapcount: can't collapse if there's a gup pin.
* The page must only be referenced by the scanned process
* and page swap cache.
*/
if (page_count(page) != 1 + !!PageSwapCache(page)) {
unlock_page(page);
goto out;
}
if (pte_write(pteval)) {
writable = true;
} else {
if (PageSwapCache(page) && !reuse_swap_page(page)) {
unlock_page(page);
goto out;
}
/*
* Page is not in the swap cache. It can be collapsed
* into a THP.
*/
}
/*
* Isolate the page to avoid collapsing an hugepage
* currently in use by the VM.
*/
if (isolate_lru_page(page)) {
unlock_page(page);
goto out;
}
/* 0 stands for page_is_file_cache(page) == false */
inc_zone_page_state(page, NR_ISOLATED_ANON + 0);
VM_BUG_ON_PAGE(!PageLocked(page), page);
VM_BUG_ON_PAGE(PageLRU(page), page);
/* If there is no mapped pte young don't collapse the page */
if (pte_young(pteval) || PageReferenced(page) ||
mmu_notifier_test_young(vma->vm_mm, address))
referenced = true;
}
if (likely(referenced && writable))
return 1;
out:
release_pte_pages(pte, _pte);
return 0;
}
static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
struct vm_area_struct *vma,
unsigned long address,
spinlock_t *ptl)
{
pte_t *_pte;
for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) {
pte_t pteval = *_pte;
struct page *src_page;
if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
clear_user_highpage(page, address);
add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
if (is_zero_pfn(pte_pfn(pteval))) {
/*
* ptl mostly unnecessary.
*/
spin_lock(ptl);
/*
* paravirt calls inside pte_clear here are
* superfluous.
*/
pte_clear(vma->vm_mm, address, _pte);
spin_unlock(ptl);
}
} else {
src_page = pte_page(pteval);
copy_user_highpage(page, src_page, address, vma);
VM_BUG_ON_PAGE(page_mapcount(src_page) != 1, src_page);
release_pte_page(src_page);
/*
* ptl mostly unnecessary, but preempt has to
* be disabled to update the per-cpu stats
* inside page_remove_rmap().
*/
spin_lock(ptl);
/*
* paravirt calls inside pte_clear here are
* superfluous.
*/
pte_clear(vma->vm_mm, address, _pte);
page_remove_rmap(src_page);
spin_unlock(ptl);
free_page_and_swap_cache(src_page);
}
address += PAGE_SIZE;
page++;
}
}
static void khugepaged_alloc_sleep(void)
{
wait_event_freezable_timeout(khugepaged_wait, false,
msecs_to_jiffies(khugepaged_alloc_sleep_millisecs));
}
static int khugepaged_node_load[MAX_NUMNODES];
static bool khugepaged_scan_abort(int nid)
{
int i;
/*
* If zone_reclaim_mode is disabled, then no extra effort is made to
* allocate memory locally.
*/
if (!zone_reclaim_mode)
return false;
/* If there is a count for this node already, it must be acceptable */
if (khugepaged_node_load[nid])
return false;
for (i = 0; i < MAX_NUMNODES; i++) {
if (!khugepaged_node_load[i])
continue;
if (node_distance(nid, i) > RECLAIM_DISTANCE)
return true;
}
return false;
}
#ifdef CONFIG_NUMA
static int khugepaged_find_target_node(void)
{
static int last_khugepaged_target_node = NUMA_NO_NODE;
int nid, target_node = 0, max_value = 0;
/* find first node with max normal pages hit */
for (nid = 0; nid < MAX_NUMNODES; nid++)
if (khugepaged_node_load[nid] > max_value) {
max_value = khugepaged_node_load[nid];
target_node = nid;
}
/* do some balance if several nodes have the same hit record */
if (target_node <= last_khugepaged_target_node)
for (nid = last_khugepaged_target_node + 1; nid < MAX_NUMNODES;
nid++)
if (max_value == khugepaged_node_load[nid]) {
target_node = nid;
break;
}
last_khugepaged_target_node = target_node;
return target_node;
}
static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
{
if (IS_ERR(*hpage)) {
if (!*wait)
return false;
*wait = false;
*hpage = NULL;
khugepaged_alloc_sleep();
} else if (*hpage) {
put_page(*hpage);
*hpage = NULL;
}
return true;
}
static struct page *
khugepaged_alloc_page(struct page **hpage, gfp_t gfp, struct mm_struct *mm,
struct vm_area_struct *vma, unsigned long address,
int node)
{
VM_BUG_ON_PAGE(*hpage, *hpage);
/*
* Before allocating the hugepage, release the mmap_sem read lock.
* The allocation can take potentially a long time if it involves
* sync compaction, and we do not need to hold the mmap_sem during
* that. We will recheck the vma after taking it again in write mode.
*/
up_read(&mm->mmap_sem);
*hpage = alloc_pages_exact_node(node, gfp, HPAGE_PMD_ORDER);
if (unlikely(!*hpage)) {
count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
*hpage = ERR_PTR(-ENOMEM);
return NULL;
}
count_vm_event(THP_COLLAPSE_ALLOC);
return *hpage;
}
#else
static int khugepaged_find_target_node(void)
{
return 0;
}
static inline struct page *alloc_hugepage(int defrag)
{
return alloc_pages(alloc_hugepage_gfpmask(defrag, 0),
HPAGE_PMD_ORDER);
}
static struct page *khugepaged_alloc_hugepage(bool *wait)
{
struct page *hpage;
do {
hpage = alloc_hugepage(khugepaged_defrag());
if (!hpage) {
count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
if (!*wait)
return NULL;
*wait = false;
khugepaged_alloc_sleep();
} else
count_vm_event(THP_COLLAPSE_ALLOC);
} while (unlikely(!hpage) && likely(khugepaged_enabled()));
return hpage;
}
static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
{
if (!*hpage)
*hpage = khugepaged_alloc_hugepage(wait);
if (unlikely(!*hpage))
return false;
return true;
}
static struct page *
khugepaged_alloc_page(struct page **hpage, gfp_t gfp, struct mm_struct *mm,
struct vm_area_struct *vma, unsigned long address,
int node)
{
up_read(&mm->mmap_sem);
VM_BUG_ON(!*hpage);
return *hpage;
}
#endif
static bool hugepage_vma_check(struct vm_area_struct *vma)
{
if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
(vma->vm_flags & VM_NOHUGEPAGE))
return false;
if (!vma->anon_vma || vma->vm_ops)
return false;
if (is_vma_temporary_stack(vma))
return false;
VM_BUG_ON_VMA(vma->vm_flags & VM_NO_THP, vma);
return true;
}
static void collapse_huge_page(struct mm_struct *mm,
unsigned long address,
struct page **hpage,
struct vm_area_struct *vma,
int node)
{
pmd_t *pmd, _pmd;
pte_t *pte;
pgtable_t pgtable;
struct page *new_page;
spinlock_t *pmd_ptl, *pte_ptl;
int isolated;
unsigned long hstart, hend;
struct mem_cgroup *memcg;
unsigned long mmun_start; /* For mmu_notifiers */
unsigned long mmun_end; /* For mmu_notifiers */
gfp_t gfp;
VM_BUG_ON(address & ~HPAGE_PMD_MASK);
/* Only allocate from the target node */
gfp = alloc_hugepage_gfpmask(khugepaged_defrag(), __GFP_OTHER_NODE) |
__GFP_THISNODE;
/* release the mmap_sem read lock. */
new_page = khugepaged_alloc_page(hpage, gfp, mm, vma, address, node);
if (!new_page)
return;
if (unlikely(mem_cgroup_try_charge(new_page, mm,
gfp, &memcg)))
return;
/*
* Prevent all access to pagetables with the exception of
* gup_fast later hanlded by the ptep_clear_flush and the VM
* handled by the anon_vma lock + PG_lock.
*/
down_write(&mm->mmap_sem);
if (unlikely(khugepaged_test_exit(mm)))
goto out;
vma = find_vma(mm, address);
if (!vma)
goto out;
hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
hend = vma->vm_end & HPAGE_PMD_MASK;
if (address < hstart || address + HPAGE_PMD_SIZE > hend)
goto out;
if (!hugepage_vma_check(vma))
goto out;
pmd = mm_find_pmd(mm, address);
if (!pmd)
goto out;
anon_vma_lock_write(vma->anon_vma);
pte = pte_offset_map(pmd, address);
pte_ptl = pte_lockptr(mm, pmd);
mmun_start = address;
mmun_end = address + HPAGE_PMD_SIZE;
mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */
/*
* After this gup_fast can't run anymore. This also removes
* any huge TLB entry from the CPU so we won't allow
* huge and small TLB entries for the same virtual address
* to avoid the risk of CPU bugs in that area.
*/
_pmd = pmdp_clear_flush(vma, address, pmd);
spin_unlock(pmd_ptl);
mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
spin_lock(pte_ptl);
isolated = __collapse_huge_page_isolate(vma, address, pte);
spin_unlock(pte_ptl);
if (unlikely(!isolated)) {
pte_unmap(pte);
spin_lock(pmd_ptl);
BUG_ON(!pmd_none(*pmd));
/*
* We can only use set_pmd_at when establishing
* hugepmds and never for establishing regular pmds that
* points to regular pagetables. Use pmd_populate for that
*/
pmd_populate(mm, pmd, pmd_pgtable(_pmd));
spin_unlock(pmd_ptl);
anon_vma_unlock_write(vma->anon_vma);
goto out;
}
/*
* All pages are isolated and locked so anon_vma rmap
* can't run anymore.
*/
anon_vma_unlock_write(vma->anon_vma);
__collapse_huge_page_copy(pte, new_page, vma, address, pte_ptl);
pte_unmap(pte);
__SetPageUptodate(new_page);
pgtable = pmd_pgtable(_pmd);
_pmd = mk_huge_pmd(new_page, vma->vm_page_prot);
_pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
/*
* spin_lock() below is not the equivalent of smp_wmb(), so
* this is needed to avoid the copy_huge_page writes to become
* visible after the set_pmd_at() write.
*/
smp_wmb();
spin_lock(pmd_ptl);
BUG_ON(!pmd_none(*pmd));
page_add_new_anon_rmap(new_page, vma, address);
mem_cgroup_commit_charge(new_page, memcg, false);
lru_cache_add_active_or_unevictable(new_page, vma);
pgtable_trans_huge_deposit(mm, pmd, pgtable);
set_pmd_at(mm, address, pmd, _pmd);
update_mmu_cache_pmd(vma, address, pmd);
spin_unlock(pmd_ptl);
*hpage = NULL;
khugepaged_pages_collapsed++;
out_up_write:
up_write(&mm->mmap_sem);
return;
out:
mem_cgroup_cancel_charge(new_page, memcg);
goto out_up_write;
}
static int khugepaged_scan_pmd(struct mm_struct *mm,
struct vm_area_struct *vma,
unsigned long address,
struct page **hpage)
{
pmd_t *pmd;
pte_t *pte, *_pte;
int ret = 0, none_or_zero = 0;
struct page *page;
unsigned long _address;
spinlock_t *ptl;
int node = NUMA_NO_NODE;
bool writable = false, referenced = false;
VM_BUG_ON(address & ~HPAGE_PMD_MASK);
pmd = mm_find_pmd(mm, address);
if (!pmd)
goto out;
memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load));
pte = pte_offset_map_lock(mm, pmd, address, &ptl);
for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
_pte++, _address += PAGE_SIZE) {
pte_t pteval = *_pte;
if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
if (++none_or_zero <= khugepaged_max_ptes_none)
continue;
else
goto out_unmap;
}
if (!pte_present(pteval))
goto out_unmap;
if (pte_write(pteval))
writable = true;
page = vm_normal_page(vma, _address, pteval);
if (unlikely(!page))
goto out_unmap;
/*
* Record which node the original page is from and save this
* information to khugepaged_node_load[].
* Khupaged will allocate hugepage from the node has the max
* hit record.
*/
node = page_to_nid(page);
if (khugepaged_scan_abort(node))
goto out_unmap;
khugepaged_node_load[node]++;
VM_BUG_ON_PAGE(PageCompound(page), page);
if (!PageLRU(page) || PageLocked(page) || !PageAnon(page))
goto out_unmap;
/*
* cannot use mapcount: can't collapse if there's a gup pin.
* The page must only be referenced by the scanned process
* and page swap cache.
*/
if (page_count(page) != 1 + !!PageSwapCache(page))
goto out_unmap;
if (pte_young(pteval) || PageReferenced(page) ||
mmu_notifier_test_young(vma->vm_mm, address))
referenced = true;
}
if (referenced && writable)
ret = 1;
out_unmap:
pte_unmap_unlock(pte, ptl);
if (ret) {
node = khugepaged_find_target_node();
/* collapse_huge_page will return with the mmap_sem released */
collapse_huge_page(mm, address, hpage, vma, node);
}
out:
return ret;
}
static void collect_mm_slot(struct mm_slot *mm_slot)
{
struct mm_struct *mm = mm_slot->mm;
VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
if (khugepaged_test_exit(mm)) {
/* free mm_slot */
hash_del(&mm_slot->hash);
list_del(&mm_slot->mm_node);
/*
* Not strictly needed because the mm exited already.
*
* clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
*/
/* khugepaged_mm_lock actually not necessary for the below */
free_mm_slot(mm_slot);
mmdrop(mm);
}
}
static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
struct page **hpage)
__releases(&khugepaged_mm_lock)
__acquires(&khugepaged_mm_lock)
{
struct mm_slot *mm_slot;
struct mm_struct *mm;
struct vm_area_struct *vma;
int progress = 0;
VM_BUG_ON(!pages);
VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
if (khugepaged_scan.mm_slot)
mm_slot = khugepaged_scan.mm_slot;
else {
mm_slot = list_entry(khugepaged_scan.mm_head.next,
struct mm_slot, mm_node);
khugepaged_scan.address = 0;
khugepaged_scan.mm_slot = mm_slot;
}
spin_unlock(&khugepaged_mm_lock);
mm = mm_slot->mm;
down_read(&mm->mmap_sem);
if (unlikely(khugepaged_test_exit(mm)))
vma = NULL;
else
vma = find_vma(mm, khugepaged_scan.address);
progress++;
for (; vma; vma = vma->vm_next) {
unsigned long hstart, hend;
cond_resched();
if (unlikely(khugepaged_test_exit(mm))) {
progress++;
break;
}
if (!hugepage_vma_check(vma)) {
skip:
progress++;
continue;
}
hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
hend = vma->vm_end & HPAGE_PMD_MASK;
if (hstart >= hend)
goto skip;
if (khugepaged_scan.address > hend)
goto skip;
if (khugepaged_scan.address < hstart)
khugepaged_scan.address = hstart;
VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
while (khugepaged_scan.address < hend) {
int ret;
cond_resched();
if (unlikely(khugepaged_test_exit(mm)))
goto breakouterloop;
VM_BUG_ON(khugepaged_scan.address < hstart ||
khugepaged_scan.address + HPAGE_PMD_SIZE >
hend);
ret = khugepaged_scan_pmd(mm, vma,
khugepaged_scan.address,
hpage);
/* move to next address */
khugepaged_scan.address += HPAGE_PMD_SIZE;
progress += HPAGE_PMD_NR;
if (ret)
/* we released mmap_sem so break loop */
goto breakouterloop_mmap_sem;
if (progress >= pages)
goto breakouterloop;
}
}
breakouterloop:
up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
breakouterloop_mmap_sem:
spin_lock(&khugepaged_mm_lock);
VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
/*
* Release the current mm_slot if this mm is about to die, or
* if we scanned all vmas of this mm.
*/
if (khugepaged_test_exit(mm) || !vma) {
/*
* Make sure that if mm_users is reaching zero while
* khugepaged runs here, khugepaged_exit will find
* mm_slot not pointing to the exiting mm.
*/
if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
khugepaged_scan.mm_slot = list_entry(
mm_slot->mm_node.next,
struct mm_slot, mm_node);
khugepaged_scan.address = 0;
} else {
khugepaged_scan.mm_slot = NULL;
khugepaged_full_scans++;
}
collect_mm_slot(mm_slot);
}
return progress;
}
static int khugepaged_has_work(void)
{
return !list_empty(&khugepaged_scan.mm_head) &&
khugepaged_enabled();
}
static int khugepaged_wait_event(void)
{
return !list_empty(&khugepaged_scan.mm_head) ||
kthread_should_stop();
}
static void khugepaged_do_scan(void)
{
struct page *hpage = NULL;
unsigned int progress = 0, pass_through_head = 0;
unsigned int pages = khugepaged_pages_to_scan;
bool wait = true;
barrier(); /* write khugepaged_pages_to_scan to local stack */
while (progress < pages) {
if (!khugepaged_prealloc_page(&hpage, &wait))
break;
cond_resched();
if (unlikely(kthread_should_stop() || freezing(current)))
break;
spin_lock(&khugepaged_mm_lock);
if (!khugepaged_scan.mm_slot)
pass_through_head++;
if (khugepaged_has_work() &&
pass_through_head < 2)
progress += khugepaged_scan_mm_slot(pages - progress,
&hpage);
else
progress = pages;
spin_unlock(&khugepaged_mm_lock);
}
if (!IS_ERR_OR_NULL(hpage))
put_page(hpage);
}
static void khugepaged_wait_work(void)
{
try_to_freeze();
if (khugepaged_has_work()) {
if (!khugepaged_scan_sleep_millisecs)
return;
wait_event_freezable_timeout(khugepaged_wait,
kthread_should_stop(),
msecs_to_jiffies(khugepaged_scan_sleep_millisecs));
return;
}
if (khugepaged_enabled())
wait_event_freezable(khugepaged_wait, khugepaged_wait_event());
}
static int khugepaged(void *none)
{
struct mm_slot *mm_slot;
set_freezable();
set_user_nice(current, MAX_NICE);
while (!kthread_should_stop()) {
khugepaged_do_scan();
khugepaged_wait_work();
}
spin_lock(&khugepaged_mm_lock);
mm_slot = khugepaged_scan.mm_slot;
khugepaged_scan.mm_slot = NULL;
if (mm_slot)
collect_mm_slot(mm_slot);
spin_unlock(&khugepaged_mm_lock);
return 0;
}
static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
unsigned long haddr, pmd_t *pmd)
{
struct mm_struct *mm = vma->vm_mm;
pgtable_t pgtable;
pmd_t _pmd;
int i;
pmdp_clear_flush_notify(vma, haddr, pmd);
/* leave pmd empty until pte is filled */
pgtable = pgtable_trans_huge_withdraw(mm, pmd);
pmd_populate(mm, &_pmd, pgtable);
for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
pte_t *pte, entry;
entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
entry = pte_mkspecial(entry);
pte = pte_offset_map(&_pmd, haddr);
VM_BUG_ON(!pte_none(*pte));
set_pte_at(mm, haddr, pte, entry);
pte_unmap(pte);
}
smp_wmb(); /* make pte visible before pmd */
pmd_populate(mm, pmd, pgtable);
put_huge_zero_page();
}
void __split_huge_page_pmd(struct vm_area_struct *vma, unsigned long address,
pmd_t *pmd)
{
spinlock_t *ptl;
struct page *page;
struct mm_struct *mm = vma->vm_mm;
unsigned long haddr = address & HPAGE_PMD_MASK;
unsigned long mmun_start; /* For mmu_notifiers */
unsigned long mmun_end; /* For mmu_notifiers */
BUG_ON(vma->vm_start > haddr || vma->vm_end < haddr + HPAGE_PMD_SIZE);
mmun_start = haddr;
mmun_end = haddr + HPAGE_PMD_SIZE;
again:
mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
ptl = pmd_lock(mm, pmd);
if (unlikely(!pmd_trans_huge(*pmd))) {
spin_unlock(ptl);
mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
return;
}
if (is_huge_zero_pmd(*pmd)) {
__split_huge_zero_page_pmd(vma, haddr, pmd);
spin_unlock(ptl);
mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
return;
}
page = pmd_page(*pmd);
VM_BUG_ON_PAGE(!page_count(page), page);
get_page(page);
spin_unlock(ptl);
mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
split_huge_page(page);
put_page(page);
/*
* We don't always have down_write of mmap_sem here: a racing
* do_huge_pmd_wp_page() might have copied-on-write to another
* huge page before our split_huge_page() got the anon_vma lock.
*/
if (unlikely(pmd_trans_huge(*pmd)))
goto again;
}
void split_huge_page_pmd_mm(struct mm_struct *mm, unsigned long address,
pmd_t *pmd)
{
struct vm_area_struct *vma;
vma = find_vma(mm, address);
BUG_ON(vma == NULL);
split_huge_page_pmd(vma, address, pmd);
}
static void split_huge_page_address(struct mm_struct *mm,
unsigned long address)
{
pgd_t *pgd;
pud_t *pud;
pmd_t *pmd;
VM_BUG_ON(!(address & ~HPAGE_PMD_MASK));
pgd = pgd_offset(mm, address);
if (!pgd_present(*pgd))
return;
pud = pud_offset(pgd, address);
if (!pud_present(*pud))
return;
pmd = pmd_offset(pud, address);
if (!pmd_present(*pmd))
return;
/*
* Caller holds the mmap_sem write mode, so a huge pmd cannot
* materialize from under us.
*/
split_huge_page_pmd_mm(mm, address, pmd);
}
void __vma_adjust_trans_huge(struct vm_area_struct *vma,
unsigned long start,
unsigned long end,
long adjust_next)
{
/*
* If the new start address isn't hpage aligned and it could
* previously contain an hugepage: check if we need to split
* an huge pmd.
*/
if (start & ~HPAGE_PMD_MASK &&
(start & HPAGE_PMD_MASK) >= vma->vm_start &&
(start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
split_huge_page_address(vma->vm_mm, start);
/*
* If the new end address isn't hpage aligned and it could
* previously contain an hugepage: check if we need to split
* an huge pmd.
*/
if (end & ~HPAGE_PMD_MASK &&
(end & HPAGE_PMD_MASK) >= vma->vm_start &&
(end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
split_huge_page_address(vma->vm_mm, end);
/*
* If we're also updating the vma->vm_next->vm_start, if the new
* vm_next->vm_start isn't page aligned and it could previously
* contain an hugepage: check if we need to split an huge pmd.
*/
if (adjust_next > 0) {
struct vm_area_struct *next = vma->vm_next;
unsigned long nstart = next->vm_start;
nstart += adjust_next << PAGE_SHIFT;
if (nstart & ~HPAGE_PMD_MASK &&
(nstart & HPAGE_PMD_MASK) >= next->vm_start &&
(nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
split_huge_page_address(next->vm_mm, nstart);
}
}
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